The baby boomers have finally been eclipsed by an even bigger generation.

Boomers – those born between 1946 and 1964 – now fall just short of being the largest living age group in the United States. They number 74.9 million, as compared to the 75.4 million Millennials, who are defined as those born between 1981 and 1997, according to Pew Research Center data released in conjunction with the US Census Bureau earlier this month.

The US Millennial population will continue to grow, thanks to the arrival of immigrants between the ages of 18 and 24, Pew noted. With continued immigration, the Millennial population is expected to peak at 81 million in 2036. About a quarter of the US Hispanic population, and nearly half of its voters, are Millennials; 32 percent are younger than 18.

This influx of immigrants has helped shaped Millennials' views on immigration. In March, Pew found a stark generational divide on immigration attitudes: 76 percent of Millennials agreed that "immigrants strengthen the country because of their hard work and talents," compared with 60 percent of Gen Xers and 48 percent of Boomers.

That's a position that correlates with liberal political views, according to Pew: 78 percent of Democrats or Democrat-leaning Americans agree that immigrants make America stronger, versus 35 percent of Republicans and Republican-leaning Americans.

Immigration is not the only topic on which Millennials are further to the political left than the general US population. A 2014 study by Pew found that Millennials are more liberal on a wide range of social issues including marijuana legalization, interracial marriage, and same-sex marriage, although they tend to be more like their elders views on gun control and abortion, and are actually more likely to say that increased single parenthood is bad for society.

Millennials' liberalism may spell trouble for the future of the Republican party. About half of Millennials, Pew found in 2014, are Democrats or Democratic-leaning, compared to just 34 percent who affiliate or lean toward the GOP. Boomers, on the other hand, are close to being evenly divided between the two parties. Millennial Republicans tend to be less conservative than older ones, with more than half believing that homosexuality should be accepted and that immigrants improve the country.

Millennials on average also tend to lean left on economic issues, perhaps a result of having to carry heavier financial burdens than their immediate forebears did. 71 percent of Millennials making less than $20,000 per year believe "the government should spend more on financial assistance to the poor, even if it leads to higher taxes." Among their generational peers making more than $100,000 per year, however, that drops to 45 percent.

A YouGov poll in January 2016 found that 43 percent of Millennials also have a favorable opinion of socialism, versus 29 percent of the population as a whole.

Still, as the Washington Post's Emily Ekins argued in March, Millennials' blue hue may fade over time. She cites a Reason-Rupe poll that found that, as Millennials reach the threshold of earning $40,000 to $60,000 a year, they tend to oppose income redistribution. Ms. Ekins also points out that Boomers in the 80s and Gen Xers in the 90s also supported big government, but grew more skeptical over time.